The present invention relates to vehicle transmission shifters with actuators incorporating a shape memory alloy wire and/or incorporating a magnetic lock/unlock mechanism to control movement of a shift lever, and more particularly relates to a shifter with shape memory alloy wire actuator and/or magnetic lock/unlock mechanism for controlling movement of a pawl out of a “park” position notch. However, it is contemplated that the present concept is not limited to only vehicle shifters with pawls, nor to only park lock systems, but instead is applicable for any lock/unlock mechanism where a blocking member must be selectively moved with an actuator while occupying a minimum of space and preferably where the actuating mechanism has a minimum of components.
In brake transmission shift interlock mechanisms in automotive shift systems, it is desirable to either block the shift lever itself or block the shift lever's actuating pawl to prevent shifting of the shift lever from the Park position until the ignition key is in the “on” or “run” position and the brake is depressed. However, in an effort to provide these functions, shifters have often become complex, and relatively expensive components are used. Thus, component costs and manufacturing costs have increased significantly. For example, solenoids are often used to control movement of a park lock member that prevents the shifter's pawl from being removed from the Park position. However, solenoids are not inexpensive since they include copper coils and are associated with electromagnetic fields. Further, they require all of the operations associated with coiling insulated copper wire, stripping and terminating coils, electrically connecting the wires to a power source, assembling the solenoid as a preassembled unit, and assembling the solenoid into a shifter. Also, they can create electromagnetic fields and/or voltage spikes that cause disruption to a vehicle's electrical system. For example, some recent shifters incorporate an electrical-actuator-driven pawl onto the shift lever for controlling movement of the shift lever. These actuator-driven pawls typically include a solenoid or electromechanical device operably connected to the pawl member for moving the pawl member into and out of notches representing gear positions. Still further, coils require a significant amount of dimensional space. Recent shifter designs are requiring a reduction in the three-dimensional space occupied by the shifters, and by the shift lock mechanisms. Still further, a force of solenoids varies considerably depending on their temperature. It is desirable to provide a constant force actuator that is not sensitive to temperature.
It is desirable to produce an improved simple, cost-effective electrical actuating device that does not require the complexity of copper coils and associated electromagnetic fields, does not require electromagnetic field collapse energy and associated voltage spikes, and that does not require mechanical processing associated with coiling insulated copper wire, stripping and terminating coils. Further, a smaller design package is desired.
At the same time, pawl-engaging park-lock mechanisms in shifters sometimes require an extra force to initiate movement of the blocking member. This can be caused by a number of different things, such as initial mechanical static friction, by excess friction caused by the vehicle driver pulling on the shifter lever or pawl prior to movement of the blocking member, and other reasons. A compact arrangement is desired that provides an initial high-energy “kick” force to initiate movement of the blocking member, yet that fits within a very small dimensional space, and at the same time that does not result in damage to components when movement of the blocking member is temporarily not possible.